1. Field of The Invention
This invention relates to a wiper device having a wiper arm which has a wiper blade and is used for wiping a windshield by moving in an oscillatory mode on the windshield by means of a driving motor.
2. Description of The Prior Art
Heretofore, there has been used a wiper device as shown in FIG. 5 to FIG. 7, for example.
In the wiper device shown in the figures, an output shaft 51 of a motor 50 is connected through a linkage L (not shown) to a wiper pivot 54 fixed on a panel 53 of a vehicle body on the lower side of a hood 52 in FIG. 5, and said wiper pivot 54 is attached with a wiper arm 100 provided with an arm head 101 and a retainer 102.
Said arm head 101 is attached with the retainer 102 through a shaft 103 and can be pivoted upwardly in order to keep the retainer in a "lock-back" state, and with a coil spring 105 connected with a connector 104 and stretched from a pin 101a provided to the arm head 101 over a hook 102a provided to the retainer 102.
The retainer 102 is so designed as to attach a wiper blade at the top end thereof (see FIG. 6), and so structured as to press the wiper blade 55 onto a windshield 56 by the tension of the coil spring 105 provided to the wiper arm 100.
Additionally, said "lock-back" means maintains the retainer of the wiper arm pivoted upwardly and keeps the wiper blade attached to the retainer from the wiped surface on the windshield in case of snowfall, freezing or during car washing, for example.
An electric circuit to be connected with said wiper device will be described below on basis of a schematic circuit diagram shown in FIG. 7. A terminal 57 of the motor 50 is connected to a contact of a wiper switch 110 and another contact of said wiper switch 110 is connected to one of contacts of an ignition switch 111, furthermore another contact of said ignition switch 111 is connected to a power source 112 and another terminal 58 of the motor 50 is grounded.
Upon, switching on the wiper switch 110 when the ignition switch 111 is in the ON-state, the power source 112 is connected to the motor 50 and an output shaft 51 of the motor 50 rotates.
By the rotation of the output shaft 51 of the motor 50, the rotational motion of the output shaft 51 is converted into the reciprocative rotation of the wiper pivot 54, thereby the wiper arm 100 oscillates round the wiper pivot 54 as the center on the windshield 56 and makes the wiper blade 55 in wiping operation between position A and B.
Upon, switching off the wiper switch 110, the ouput shaft 51 of the motor 50 rotates in the reverse direction by a wiper blade-housing mechanism (not shown) provided to the motor 50 and when the wiper blade 55 arrives at a position A on the windshield 56, the wiper blade 55 shifts to a position C lower than the position A on the windshield 56 and is housed in the lower side of the hood 52.
In case of making the wiper arm 100 in the "lock-back" state in order to exchange the wiper blade 55, or to prevent the wiper blade 55 from adherence owing to freezing by keeping the wiper balde 55 apart from the windshield 56, the wiper blade 55 can be stopped at a position on the way by switching off the ignition switch 111 when the wiper blade 55 shifts to a position near to the position B above the position A on the windshield 56 by switching on the wiper switch 110 once after switching on the ignition switch 110.
Then, the retainer 102 and the wiper blade 55 are detached from the windshield 56 by raising the retainer 102 of the wiper arm 100 up to the position shown with two-dot chain lines in FIG. 5 around the shaft 103 of the arm head 101 as the center point, and become locked in this position because a point of action the other side of the shaft 103 toward the hood 52.
However, since the conventional wiper device described above has no means for detecting whether or not the wiper arm is in the "lock-back" state, switching on the wiper switch 110 at a state in which the ignition switch 111 is switched on and the wiper arm 100 remains in the "lock-back" state, the output shaft 51 of the motor 50 rotates in the reverse direction in order to shift the wiper blade 55 to the position C on the windshield and to house it in the lower side of the hood 52 by the wiper blade housing mechanism (not shown) of the motor 50. Therefore there is a problem since the wiper blade 55 or the wiper arm 100 hits against the hood 52 and damages the hood 52.